Before reading this -you must agree -there will be no jokes of snickering about my photography or graphics.
This is not really copper braiding a spring, but I call it that because everyone knows what copper braiding a spring means. This is a real simple modification that can make a big difference in the output of a high power P60 - or - it may make no difference at all, depending on your host. It seems, everyone knows to braid the switch spring and the positive P60 contact spring, but the easiest spring to make a really good conductor is the outer P60 spring (in the future, this spring will be referred to as ‘the big spring’) If your host doesn’t have a good electrical path from the thermal wrapping around the drop in to the battery, it may be depending on the big spring to complete the negative path. You will have to look at your host to determine if you need this spring enhancement. If the head unscrews from the battery tube, and the threads are anodized…you need it. If you have a solarforce and you use aluminum foil or copper foil to wrap tightly…you don’t need it. If you have a 502B -you definitely need it.
If you’re unsure if you need it or not, do it anyway -it’s just that easy:
A pictures’ worth a thousand words -in my case, it may be worth two thousand:
I used a piece of 2mil copper foil about 3/16” wide by 2” long. Look at the photo at the wrap direction around the spring -the second drawing shows a cutaway view. The loop that will be your contact point at the bottom of the spring should be close to the cut end of the spring. Make sure the cut end of the spring does not have a burr on the bottom edge, if it does, file it off.
This copper strip will create a very short, very conductive negative return path from the pill to the host.
Remove the spring
Cut a strip of copper foil about 3/16” x 2”
Slip the copper strip around the bottom coil of the spring with both ends pointed towards the outside of the spring
Take the two ends and slip them under and around the top coil of the spring as shown.
Leave the ends of the copper strip long and fold it down the outside of the spring.
Grip the spring with thumb and forefinger -one of the fingers should be pressing on the copper strips to keep them in place
Put the spring on as usual
Rotate the spring until the copper loop on the bottom is close to the cut end of the spring
Cut the excess ends off of the copper strip
Set the drop in on a table , spring side down, and make sure the copper is in a position that will make contact when the spring is compressed
Wrap and install the drop in
When you insert the drop in, the copper foil will be trapped between the flashlight body and spring coils, so it can’t make
contact with any driver components, positive spring or battery positive.
Total time to complete (not counting removing and reinstalling the drop in): 1 minute
Wrapping the drop-in with copper or aluminium foil has the same effect, you can take the larger spring off completely. It increases the thermal path to the outside of the torch as well.
Some hosts have a removable head that threads onto the battery tube. If the threads are anodized, the electrical path is not very good. Other hosts may have anodizing on the inside of the head, this is not a good electrical or thermal path. This method connects the brass pill directly to the battery tube.
I’ve tested a 502B host with a 3.04a drop in - adding this strip increases the output by about 70 lumens. It all depends on the host.
Ah, I see. I only have Solarforce L2 series P60 hosts and there is no anodising on the interior surfaces, the tailcap threads aren’t anodised but the threads at the head end are but by that time the current has got to the outer edges of the pill and reflector via the inside of the battery tube and copper or aluminium foil wrap.
I tested it in an integrating sphere while it was being powered by a lab power supply set for constant voltage (I should note, it was around 70 lumens +/- 2 or 3)…does it look brighter -(880L vs 950)? -If I looked at them side by side, I would probably have a 75% chance guessing which one is brighter…but the one thing I know for sure…‘brighter is brighter’
love all your research on p60 drop ins and another nice addition. even if it had a small increase on lumens it may have made the torch more efficient (depending on your driver)
Thanks, I just can’t stand to give up a few extra lumens.
I would like to point out, you may be able to do this with aluminum foil…I’ve never tried it. Aluminum foil tears easier, but I think it’s still doable -especially with the thicker foil.
Your right…the Solarforce battery tube and head are made in one piece with no internal anodizing. The Solarforce anodized threads on the head aren’t part of the electrical path. With the 502B, you can screw the head off of the battery tube. If you depend on the thermal wrap to carry current in a 502B, the current must travel through the internal anodizing into the head, then from the head through a set of anodized threads to reach the battery tube. The copper strip on the big spring takes the current from the pill directly to the battery tube, therefore bypassing the internal anodizing and the set of anodized threads.
With the Solarforce, there’s no reason to install this strip if the drop in is wrapped with copper or aluminum foil.
Please, never wrap a P60 with copper tape or aluminum tape.
